High shear system and process for the production of acetic anhydride

ABSTRACT

A system and method for a high shear mechanical device incorporated into a process for the production of acetic anhydride as a reactor device is shown to be capable of decreasing mass transfer limitations, thereby enhancing the process. A system for the production of acetic anhydride including the mixing of catalyst and acetic acid via a high shear device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No. 12/136,508filed on Jun. 10, 2008, now U.S. Pat. No. 7,919,645, which claims thebenefit under 35 U.S.C. §119(e) of U.S. Provisional Patent ApplicationNo. 60/946,476 filed Jun. 27, 2007, the disclosures of which are herebyincorporated herein by reference for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Technical Field

The present disclosure relates generally to the production of aceticanhydride and more particularly, to apparatus and methods enhancing theproduction of acetic anhydride. More specifically, the disclosurerelates to the reduction of mass transfer limitations of apparatus andmethods for the production of acetic anhydride.

2. Background of the Invention

Acetic anhydride is an industrial chemical reagent, widely used inorganic synthesis. Furthermore, large quantities are used, for example,in the manufacture of cellulose acetate as well as other commerciallysignificant acetylations. It has commonly been produced on an industrialscale by the reaction of ketene and acetic acid. Conventionallyprocesses for preparing acetic anhydride have been disclosed in U.S.Pat. Nos. 4,115,444; 4,252,983; 4,333,885; 4,519,956; 4,563,309; and5,488,143.

U.S. Pat. No. 7,199,263 describes a process for co-production of aceticanhydride and acetate co-production. The production of acetic anhydrideby the ketene process is conventionally known. The method comprises thethermal decomposition of acetic acid at high temperatures utilizing, forexample, triethyl phosphate dehydration catalyst to produce ketene (1)which is subsequently reacted with excess acetic acid to obtain aceticanhydride (2):CH₃COOH→H₂C═C═O+H₂O  (1)H₂C═C═O+CH₃COOH→O═CCH₃OCH₃C═O  (2)

Reaction (1) is carried out at low pressure and elevated temperature,typically in excess of 700° C. Catalyst in the product stream may beneutralized with ammonia. The process is widely employed however, it iscapital intensive. For efficient acetic anhydride production, watergenerated in reaction (1) is removed and acetic acid is recovered. Dueto the quantity of water, 1 mole of water per mole of ketene, weak acidrecovery adversely impacts operating energy costs.

Accordingly, there is a need in the industry for improved processes forthe production of acetic anhydride whereby water removal and acidrecovery are increased, so that production of acetic anhydride is morecommercially feasible.

SUMMARY OF THE INVENTION

A high shear system and method for accelerating the production of aceticanhydride is disclosed. The disclosed high shear method reduces masstransfer limitations, thereby improving reaction conditions in thereactor such as the reaction rate, temperature, pressure, time and/orproduct yield. In accordance with certain embodiments of the presentdisclosure, a method is provided that makes possible an increase in therate of acetic anhydride production by providing for more optimal time,temperature and pressure conditions than are conventionally used.

The method employs a high shear device to provide enhanced time,temperature and pressure conditions resulting in accelerated chemicalreactions between reactants.

These and other embodiments, features and advantages will be apparent inthe following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred embodiment of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

FIG. 1 is a cross-sectional diagram of a high shear device for theproduction of acetic anhydride.

FIG. 2 is a process flow diagram according to an embodiment of thepresent disclosure for a high shear system for production of aceticanhydride.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview

A system and method employs an external high shear mechanical device toprovide rapid contact and mixing of chemical ingredients in a controlledenvironment in the reactor/mixer device. The high shear device reducesthe mass transfer limitations on the reaction and thus increases theoverall reaction rate.

Chemical reactions involving liquids, gases and solids rely on the lawsof kinetics that involve time, temperature, and pressure to define therate of reactions. In cases where it is desirable to react two or moreraw materials of different phases (e.g. solid and liquid; liquid andgas; solid, liquid and gas), one of the limiting factors in controllingthe rate of reaction involves the contact time of the reactants. In thecase of heterogeneously catalyzed reactions there is the additional ratelimiting factor of having the reacted products removed from the surfaceof the catalyst to enable the catalyst to catalyze further reactants.

In conventional reactors, contact time for the reactants and/or catalystis often controlled by mixing which provides contact with two or morereactants involved in a chemical reaction. A reactor assembly thatcomprises an external high shear mixer makes possible decreased masstransfer limitations and thereby allows the reaction to more closelyapproach kinetic limitations. When reaction rates are accelerated,residence times may be decreased, thereby increasing obtainablethroughput. Alternatively, where the current yield is acceptable,decreasing the required residence time allows for the use of lowertemperatures and/or pressures than conventional processes.

High Shear Device

High shear devices (HSD) such as a high shear mixer, or high shear mill,are generally divided into classes based upon their ability to mixfluids. Mixing is the process of reducing the size of inhomogeneousspecies or particles within the fluid. One metric for the degree orthoroughness of mixing is the energy density per unit volume that themixing device generates to disrupt the fluid particles. The classes aredistinguished based on delivered energy density. There are three classesof industrial mixers having sufficient energy density to consistentlyproduce mixtures or emulsions with particle or bubble sizes in the rangeof 0 to 50 μm.

Homogenization valve systems are typically classified as high energydevices. Fluid to be processed is pumped under very high pressurethrough a narrow-gap valve into a lower pressure environment. Thepressure gradients across the valve and the resulting turbulence andcavitations act to break-up any particles in the fluid. These valvesystems are most commonly used in milk homogenization and can yieldaverage particle size range from about 0.01 μm to about 1 μm. At theother end of the spectrum are high shear mixer systems classified as lowenergy devices. These systems usually have paddles or fluid rotors thatturn at high speed in a reservoir of fluid to be processed, which inmany of the more common applications is a food product. These systemsare usually used when average particle, globule or bubble, sizes ofgreater than 20 microns are acceptable in the processed fluid.

Between low energy—high shear mixers and homogenization valve systems,in terms of the mixing energy density delivered to the fluid, arecolloid mills, which are classified as intermediate energy devices. Thetypical colloid mill configuration includes a conical or disk rotor thatis separated from a complementary, liquid-cooled stator by aclosely-controlled rotor-stator gap, which is maybe between 0.025 mm and10.0 mm. Rotors are usually driven by an electric motor through a directdrive or belt mechanism. Many colloid mills, with proper adjustment, canachieve average particle, or bubble, sizes of about 0.01 μm to about 25μm in the processed fluid. These capabilities render colloid millsappropriate for a variety of applications including colloid andoil/water-based emulsion processing such as that required for cosmetics,mayonnaise, silicone/silver amalgam formation, or roofing-tar mixing.

Referring now to FIG. 1, there is presented a schematic diagram of ahigh shear device 200. High shear device 200 comprises at least onerotor-stator combination. The rotor-stator combinations may also beknown as generators 220, 230, 240 or stages without limitation. The highshear device 200 comprises at least two generators, and most preferably,the high shear device comprises at least three generators.

The first generator 220 comprises rotor 222 and stator 227. The secondgenerator 230 comprises rotor 223, and stator 228; the third generatorcomprises rotor 224 and stator 229. For each generator 220, 230, 240 therotor is rotatably driven by input 250. The generators 220, 230, 240rotate about axis 260 in rotational direction 265. Stator 227 is fixablycoupled to the high shear device wall 255.

The generators include gaps between the rotor and the stator. The firstgenerator 220 comprises a first gap 225; the second generator 230comprises a second gap 235; and the third generator 240 comprises athird gap 245. The gaps 225, 235, 245 are between about 0.025 mm (0.01in) and 10.0 mm (0.4 in) wide. Alternatively, the process comprisesutilization of a high shear device 200 wherein the gaps 225, 235, 245are between about 0.5 mm (0.02 in) and about 2.5 mm (0.1 in). In certaininstances the gap is maintained at about 1.5 mm (0.06 in).Alternatively, the gaps 225, 235, 245 are different between generators220, 230, 240. In certain instances, the gap 225 for the first generator220 is greater than about the gap 235 for the second generator 230,which is greater than about the gap 245 for the third generator 240.

Additionally, the width of the gaps 225, 235, 245 may comprise a coarse,medium, fine, and super-fine characterization. Rotors 222, 223, and 224and stators 227, 228, and 229 may be toothed designs. Each generator maycomprise two or more sets of rotor-stator teeth, as known in the art.Rotors 222, 223, and 224 may comprise a number of rotor teethcircumferentially spaced about the circumference of each rotor. Stators227, 228, and 229 may comprise a number of stator teethcircumferentially spaced about the circumference of each stator. Inembodiments, the inner diameter of the rotor is about 11.8 cm. Inembodiments, the outer diameter of the stator is about 15.4 cm. Infurther embodiments, the rotor and stator may have an outer diameter ofabout 60 mm for the rotor, and about 64 mm for the stator.Alternatively, the rotor and stator may have alternate diameters inorder to alter the tip speed and shear pressures. In certainembodiments, each of three stages is operated with a super-finegenerator, comprising a gap of between about 0.025 mm and about 3 mm.When a feed stream 205 including solid particles is to be sent throughhigh shear device 200, the appropriate gap width is first selected foran appropriate reduction in particle size and increase in particlesurface area. In embodiments, this is beneficial for increasing catalystsurface area by shearing and dispersing the particles.

High shear device 200 is fed a reaction mixture comprising the feedstream 205. Feed stream 205 comprises an emulsion of the dispersiblephase and the continuous phase. Emulsion refers to a liquefied mixturethat contains two distinguishable substances (or phases) that will notreadily mix and dissolve together. Most emulsions have a continuousphase (or matrix), which holds therein discontinuous droplets, bubbles,and/or particles of the other phase or substance. Emulsions may behighly viscous, such as slurries or pastes, or may be foams, with tinygas bubbles suspended in a liquid. As used herein, the term “emulsion”encompasses continuous phases comprising gas bubbles, continuous phasescomprising particles (e.g., solid catalyst), continuous phasescomprising droplets of a fluid that is substantially insoluble in thecontinuous phase, and combinations thereof.

Feed stream 205 may include a particulate solid catalyst component. Feedstream 205 is pumped through the generators 220, 230, 240, such thatproduct dispersion 210 is formed. In each generator, the rotors 222,223, 224 rotate at high speed relative to the fixed stators 227, 228,229. The rotation of the rotors pumps fluid, such as the feed stream205, between the outer surface of the rotor 222 and the inner surface ofthe stator 227 creating a localized high shear condition. The gaps 225,235, 245 generate high shear forces that process the feed stream 205.The high shear forces between the rotor and stator functions to processthe feed stream 205 to create the product dispersion 210. Each generator220, 230, 240 of the high shear device 200 has interchangeablerotor-stator combinations for producing a narrow distribution of thedesired bubble size, if feedstream 205 comprises a gas, or globule size,if feedstream 205 comprises a liquid, in the product dispersion 210.

The product dispersion 210 of gas particles, or bubbles, in a liquidcomprises an emulsion. In embodiments, the product dispersion 210 maycomprise a dispersion of a previously immiscible or insoluble gas,liquid or solid into the continuous phase. The product dispersion 210has an average gas particle, or bubble, size less than about 1.5 μm;preferably the bubbles are sub-micron in diameter. In certain instances,the average bubble size is in the range from about 1.0 μm to about 0.1μm. Alternatively, the average bubble size is less than about 400 nm(0.4 μm) and most preferably less than about 100 nm (0.1 μm).

Tip speed is the velocity (m/sec) associated with the end of one or morerevolving elements that is transmitting energy to the reactants. Tipspeed, for a rotating element, is the circumferential distance traveledby the tip of the rotor per unit of time, and is generally defined bythe equation V (m/sec)=π·D·n, where V is the tip speed, D is thediameter of the rotor, in meters, and n is the rotational speed of therotor, in revolutions per second. Tip speed is thus a function of therotor diameter and the rotation rate. Also, tip speed may be calculatedby multiplying the circumferential distance transcribed by the rotortip, 2 π R, where R is the radius of the rotor (meters, for example)times the frequency of revolution (for example revolutions (meters, forexample) times the frequency of revolution (for example revolutions perminute, rpm).

For colloid mills, typical tip speeds are in excess of 23 m/sec (4500ft/min) and can exceed 40 m/sec (7900 ft/min). For the purpose of thepresent disclosure the term ‘high shear’ refers to mechanicalrotor-stator devices, such as mills or mixers, that are capable of tipspeeds in excess of 5 m/sec (1000 ft/min) and require an externalmechanically driven power device to drive energy into the stream ofproducts to be reacted. A high shear device combines high tip speedswith a very small shear gap to produce significant friction on thematerial being processed. Accordingly, a local pressure in the range ofabout 1000 MPa (about 145,000 psi) to about 1050 MPa (152,300 psi) andelevated temperatures at the tip of the shear mixer are produced duringoperation. In certain embodiments, the local pressure is at least about1034 MPa (about 150,000 psi). The local pressure further depends on thetip speed, fluid viscosity, and the rotor-stator gap during operation.

An approximation of energy input into the fluid (kW/L/min) can be madeby measuring the motor energy (kW) and fluid output (L/min). Inembodiments, the energy expenditure of a high shear device is greaterthan 1000 W/m³. In embodiments, the energy expenditure is in the rangeof from about 3000 W/m³ to about 7500 W/m³. The high shear device 200combines high tip speeds with a very small shear gap to producesignificant shear on the material. The amount of shear is typicallydependent on the viscosity of the fluid. The shear rate generated in ahigh shear device 200 may be greater than 20,000 s⁻¹. In embodiments,the shear rate generated is in the range of from 20,000 s⁻¹ to 100,000s⁻¹.

The high shear device 200 produces a gas emulsion capable of remainingdispersed at atmospheric pressure for at least about 15 minutes. For thepurpose of this disclosure, an emulsion of gas particles, or bubbles, inthe dispersed phase in product dispersion 210 that are less than 1.5 μmin diameter may comprise a micro-foam. Not to be limited by a specifictheory, it is known in emulsion chemistry that sub-micron particles, orbubbles, dispersed in a liquid undergo movement primarily throughBrownian motion effects. The bubbles in the emulsion of productdispersion 210 created by the high shear device 200 may have greatermobility through boundary layers of solid catalyst particles, therebyfacilitating and accelerating the catalytic reaction through enhancedtransport of reactants.

The rotor is set to rotate at a speed commensurate with the diameter ofthe rotor and the desired tip speed as described hereinabove. Transportresistance is reduced by incorporation of high shear device 200 suchthat the velocity of the reaction is increased by at least about 5%.Alternatively, the high shear device 200 comprises a high shear colloidmill that serves as an accelerated rate reactor (ARR). The acceleratedrate reactor comprises a single stage dispersing chamber. Theaccelerated rate reactor comprises a multiple stage inline dispersercomprising at least 2 stages.

Selection of the high shear device 200 is dependent on throughputrequirements and desired particle or bubble size in the outletdispersion 210. In certain instances, high shear device 200 comprises aDispax Reactor® of IKA® Works, Inc. Wilmington, N.C. and APV NorthAmerica, Inc. Wilmington, Mass. Model DR 2000/4, for example, comprisesa belt drive, 4M generator, PTFE sealing ring, inlet flange 1″ sanitaryclamp, outlet flange ¾″ sanitary clamp, 2 HP power, output speed of 7900rpm, flow capacity (water) approximately 300 l/h to approximately 700l/h (depending on generator), a tip speed of from 9.4 m/s to about 41m/s (about 1850 ft/min to about 8070 ft/min). Several alternative modelsare available having various inlet/outlet connections, horsepower,nominal tip speeds, output rpm, and nominal flow rate.

Without wishing to be limited to a particular theory, it is believedthat the level or degree of high shear mixing is sufficient to increaserates of mass transfer and may also produce localized non-idealconditions that enable reactions to occur that would not otherwise beexpected to occur based on Gibbs free energy predictions. Localized nonideal conditions are believed to occur within the high shear deviceresulting in increased temperatures and pressures with the mostsignificant increase believed to be in localized pressures. The increasein pressures and temperatures within the high shear device areinstantaneous and localized and quickly revert back to bulk or averagesystem conditions once exiting the high shear device. In some cases, thehigh shear mixing device induces cavitation of sufficient intensity todissociate one or more of the reactants into free radicals, which mayintensify a chemical reaction or allow a reaction to take place at lessstringent conditions than might otherwise be required. Cavitation mayalso increase rates of transport processes by producing local turbulenceand liquid micro-circulation (acoustic streaming). An overview of theapplication of cavitation phenomenon in chemical/physical processingapplications is provided by Gogate et al., “Cavitation: A technology onthe horizon,” Current Science 91 (No. 1): 35-46 (2006). The high shearmixing device of certain embodiments of the present system and methodsis operated under what is believed to be cavitation conditions effectiveto dissociate the acetic acid into free radicals exposed to catalystsfor the formation of ketene, which then form corresponding aceticanhydride product.

Description of High Shear System and Process for the Production ofAcetic Anhydride

The high shear acetic anhydride production process and system of thepresent disclosure will now be described in relation to FIG. 2 which isa flow diagram of representative high shear system 100 comprising highshear device 40. FIG. 2 illustrates the basic components of the highshear system 100 including pump 5, high shear device (HSD) 40, andketene production reactor 10. The high shear device 40 is positionedbetween pump 5 and reactor 10. High shear system 100 may furthercomprise chiller train 50 and acetic anhydride production reactor 60.

Pump 5 is used to provide a controlled flow throughout high shear device40 and high shear acetic anhydride production system 100. Pump inletstream 21 is a liquid comprising acetic acid is introduced to pump 5.Pump 5 increases the pressure of the pump inlet stream 21 to greaterthan about 203 kPa (about 2 atm); alternatively, the inlet stream 21 ispressurized to greater than about 304 kPa (about 3 atm). Additionally,pump 5 may build pressure throughout HSS 100. In this way, HSS 100combines high shear with pressure to enhance reactant intimate mixing.Preferably, all contact parts of pump 5 are stainless steel, forexample, 316 stainless steel. Pump 5 may be any suitable pump, forexample, a Dayton Pressure Booster Pump Model 2P372E, Dayton Electric Co(Niles, Ill.).

The pressurized liquid acetic acid exits pump 5 via pump exit stream 12.Pump exit stream 12 is in fluid communication with HSD inlet stream 13.In certain instances, dispersible liquid stream 22 comprising a liquidcatalyst is introduced to HSD inlet stream 13. Dispersible reactantstream 22 comprises a liquid dehydration catalyst. Any suitabledehydration catalyst known to those of skill in the art may be employed.In certain instances, the catalyst in dispersible reactant stream 22comprises triethyl phosphate dehydration catalyst. In alternativeembodiments, liquid catalyst dispersible reactant stream 22 comprisesdiammonium phosphate dehydration catalyst.

The HSD inlet stream 13 comprising a mixing of dispersible liquid stream22 and pressurized pump exit stream 12 may initiate reaction (1). Infurther instances, pump exit stream 12 and dispersible liquid stream 22are introduced separately into HSD inlet stream 13. HSD inlet stream 13feeds the dispersible reactant stream 22 and the pump exit stream 12 tothe HSD 40.

High shear device 40 serves to intimately mix the pressurized liquidacetic acid solution comprising pump outlet stream 12 with the liquidcatalyst comprising dispersible reactant stream 22. There may be aplurality of high shear devices 40 used in series, or in parallel, asknown to one skilled in the art. As discussed in detail above, the highshear device 40 is a mechanical device that utilizes, for example, astator rotor mixing head with a fixed gap between the stator and rotor.HSD 40 combines high tip speeds with a very small shear gap to producesignificant shear on the material being processed. The amount of shearwill be dependant on the viscosity of the fluid.

An emulsion of catalyst and acetic acid is formed in high shear device40. As previously described, the term “emulsion” encompasses continuousphases comprising gas bubbles, continuous phases comprising particles(e.g., solid catalyst), continuous phases comprising droplets of a fluidthat is substantially insoluble in the continuous phase, andcombinations thereof. In certain instances, the emulsion comprisesliquid acetic acid as the continuous phase and the catalyst as thedispersible phase.

The resultant emulsion comprises microglobules, or globules in thesubmicron size. In embodiments, the resultant emulsion has an meanglobule diameter of less than about 1.5 μm, preferably the mean globulediameters is from about 0.4 μm (400 nm) to about 1.5 μm. In certaininstances, the high shear mixing produces hydroglobules capable ofremaining dispersed at atmospheric pressure for about 15 minutes. Thehigh shear treatment of the catalyst and the acetic acid in the emulsionmay initiate reaction (1). In certain embodiments, most of the reactionoccurs within the HSD 40.

HSD 40 is in fluid communication with reactor 10. High shear device(HSD) outlet stream 18 comprises an emulsion of micron and/orsubmicron-sized globules, as discussed hereinabove. HSD outlet stream 18is fluidly connected to reactor inlet stream 19. HSD outlet stream andreactor inlet stream 19 may be the same stream. In certain instances,the HSD outlet stream 18 may be further processed before enteringreactor inlet stream 19. Alternatively, HSD outlet stream 18 may berecycled through the HSD 40 prior to introduction to reactor inletstream 19.

Reactor inlet stream 19 is in fluid communication with reactor 10.Reactor inlet stream 19 enters reactor 10 wherein further keteneproduction occurs according to reaction (1). Reactor 10 is any reactorsuitable for the pyrolysis of acetic acid at high temperatures toproduce ketene. Reactor 10 is operated at near atmospheric pressure.Further, reactor 10 may be used for cooling of fluid, wherein thereaction (1) occurs in high shear device 40.

The acetic acid pyrolysis tubes of reactor 10 comprise nickel-freealloys, e.g. ferrochrome alloy, chrome-aluminum steel, because nickelpromotes the formation of soot and coke, and reacts with carbon monoxideyielding a highly toxic metal carbonyl. Coke efficiency represents anefficiency loss. Conventional operating conditions furnish about 85 toabout 88% conversion, with selectivity to ketene between about 90 mol %and about 95 mol %. Furthermore, heterogeneous processes using a fixedor slurry catalyst bed of phosphoric acid derivatives and phosphates isutilized at lower temperatures to avoid deactivating the catalyst andcoking the catalyst and reactor. In embodiments, the conversion, theefficiency, and/or both are improved by the process and system of HSS100.

The heat of reaction (1) is approximately 147 kJ/mol. Optimum yields ofketene conventionally require a temperature of from about 680° C. toabout 750° C. Low pressure increases the yield, but not the efficiencyof the acetic acid pyrolysis. In embodiments, the process comprising ahigh shear device 40 for reactant mixing allows for use of lowertemperatures in reactor 10 during pyrolysis. The reaction contained inthe reactor 10 yields ketene and is removed from the reactor in keteneproduct stream 16.

Removing the water by condensation prior to forming acetic anhydride isan important step in the process. Ketene product stream 16 is processedfor conversion to acetic anhydride. Ketene product stream 16 comprisingwater enters chiller train 50. Chiller train 50 condenses water andacetic acid from the hot furnace gases in ketene product stream 16. Thecatalyst, e.g. triethyl phosphate, is neutralized in the gases of keteneproduct stream 16 with ammonia. The process condensate 51 from chillertrain 50 comprises primarily acetic acid, water, acetic anhydride, andnon-volatiles including phosphorus-containing catalyst (e.g., ammoniumphosphates) and carbon from furnace coking and ketene decomposition.Process condensate 51 may be recycled through HSS 100. Additionally,overhead may be further purified, recycled, or otherwise utilized.

Uncondensed output stream 52 from chiller train 50 is fed to anhydridereactor 60. In reactor 60, ketene is reacted with additional acetic acidstream 61 to produce crude liquid acetic anhydride stream 62 perreaction (2). In embodiments, use a HSS 100 comprising reactant mixingby a high shear device 40 allows use of lower temperature and/orpressure in reactor 10 than previously enabled. The method comprisesincorporating high shear device 40 into an established process.Incorporation of HSD 40 improves the operating conditions such astemperature, pressure, rate and production of the HSS 100 in comparisonto a process or system operated without high shear device 40.

The application of enhanced mixing of the reactants by high shear device40 potentially causes greater conversion of acetic acid to ketene insome embodiments of the process. Further, the enhanced mixing of thereactants potentiates an increase in throughput of the process stream ofthe high shear system 100. In certain instances, the high shear device40 is incorporated into an established process, thereby enabling anincrease in production (i.e., greater throughput).

In embodiments, the method and system of this disclosure enable designof a smaller and/or less capital intensive process allowing selection ofa reactor 10 having lower operating temperature and/or pressurecapability than previously possible without the incorporation of highshear device 40. In embodiments, the disclosed method reduces operatingcosts/increases production from an existing process. Alternatively, thedisclosed method may reduce capital costs for the design of newprocesses. Potential benefits of the present disclosure include, but arenot limited to, faster cycle times, increased throughput, reducedoperating costs and/or reduced capital expense due to the possibility ofdesigning smaller reactors, more effective utilization of catalystand/or operating the ketene reactor at lower temperature and/orpressure.

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, and so forth). Use ofthe term “optionally” with respect to any element of a claim is intendedto mean that the subject element is required, or alternatively, is notrequired. Both alternatives are intended to be within the scope of theclaim. Use of broader terms such as comprises, includes, having, etc.should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,and the like.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the preferred embodiments of the present invention.The discussion of a reference in the Description of Related Art is notan admission that it is prior art to the present invention, especiallyany reference that may have a publication date after the priority dateof this application. The disclosures of all patents, patentapplications, and publications cited herein are hereby incorporated byreference, to the extent they provide exemplary, procedural or otherdetails supplementary to those set forth herein.

1. A system for the production of acetic anhydride, comprising: a pumppositioned upstream of a dispersible liquid catalyst inlet; at least onehigh shear device, fluidly connected to the outlet of the pump,configured for producing an emulsion of the liquid catalyst in liquidacetic acid, wherein said at least one high shear device is configuredto produce an emulsion having an average catalyst globule diameter ofless than about 5 μm; and a pyrolysis reactor fluidly connected to anoutlet of the at least one high shear device, wherein said pyrolysisreactor is configured to produce ketene by thermal decomposition ofacetic acid.
 2. The system of claim 1 wherein the at least one highshear device comprises at least one shear generator configured forproducing a tip speed of at least 5 m/s.
 3. The system of claim 2wherein the at least one high shear device has a nominal tip speed of atleast about 23 m/s.
 4. The system of claim 2 wherein the at least onehigh shear device produces a localized pressure at the tip of at leastabout 1000 MPa.
 5. The system of claim 2 wherein the at least one highshear device is configured to produce a shear rate of greater than about20,000 s⁻¹.
 6. The system of claim 2 wherein the at least one high sheardevice is configured for an energy expenditure of at least 1000 W/m³. 7.The system of claim 1 wherein the at least one high shear device isconfigured for producing an emulsion with a mean globule diameter ofless than about 1.5 μm.
 8. The system of claim 1 further comprising atleast one heat transfer element fluidly connected with the pyrolysisreactor.
 9. The system of claim 8 wherein the heat transfer elementcomprises a chiller configured for condensing acetic acid, water, andammonia-neutralized catalyst from a gas stream comprising ketene.
 10. Asystem for the production of acetic anhydride, the system comprising: ahigh shear device, having at least one shear generator, at least oneinlet, and an outlet; a pump fluidly connected to the inlet of the highshear device; an acetic acid stream fluidly connected to the pump; aliquid catalyst stream fluidly connected to the high shear device; and apyrolysis reactor fluidly connected to the outlet of the high sheardevice.
 11. The system of claim 10, wherein the high shear devicecomprises a plurality of rotor-stator shear generators.
 12. The systemof claim 11, wherein each rotor-stator is configured to produce adifferent amount of shear.
 13. The system of claim 10, wherein the highshear device is configured to produce a shear rate of greater than about20,000 s⁻¹.
 14. The system of claim 10 wherein the at least one highshear device is configured for an energy expenditure of at least 1000W/m³.
 15. The system of claim 10, wherein the pyrolysis reactor isconfigured to produce ketene by thermal decomposition of acetic acid inan emulsion with a mean globule diameter of less than about 1.5 μm. 16.A system for the production of acetic anhydride, comprising: a highshear device configured to process liquid catalyst and liquid aceticacid, wherein the high shear device operates to produce an emulsion ofliquid catalyst and liquid acetic acid, and wherein the emulsion has anaverage catalyst globule diameter of less than about 5 μm; a reactorfluidly connected to an outlet of the high shear device, wherein thereactor is operable at conditions to promote a reaction of acetic acidin the emulsion that produce a product stream comprising ketene; and asecond reactor fluidly connected with the reactor, wherein at least partof the product stream is transferred to the second reactor, and whereinat least some ketene in the second reactor reacts to produce aceticanhydride.
 17. The system of claim 16, wherein the liquid catalyst istriethyl phosphate.
 18. The system of claim 16, wherein the reaction ofacetic acid is a heterogeneous catalytic reaction.
 19. The system ofclaim 16, wherein the at least one high shear device comprises a rotorand a stator.
 20. The system of claim 19, wherein the at least one highshear device is operable to produce a localized pressure at a tip of therotor of at least about 1000 MPa.